In fluid mixing systems, particularly where plastic materials are being mixed for use in a liquid injection molding apparatus, it is often desirable that large amounts of the mixed plastic be delivered to the molds in a relatively short time period. Thus, a typical present day apparatus is capable of delivering as high as 10 to 12 lbs. of a mixture of liquid plastics to a mold in 4 to 5 seconds. Such machines are relatively large in size and are costly to manufacture and are limited in their shot capacities, that is, their abilities to deliver more than 10 to 12 pounds of liquid plastic to a mold over a reasonably short time period. In many applications, however, it is desirable that apparatus having shot capacities much higher than 10 to 12 pounds be available and that the total amount thereof be delivered in much shorter time periods, at higher flow rates. It is further desirable that the manufacturing costs and the size of apparatus which can deliver large amounts of mixed fluid plastics at high flow rates be reduced in comparison with presently available apparatus so that smaller initial capital investments are required. Moreover, the apparatus should also be capable of being installed and used with much less difficulty and greater reliability than present apparatus. Further, such apparatus should be capable of handling a wide range of different fluids having a wide range of viscosities. Moreover, such apparatus should be capable of having its operation adjustable so that variable output flow rates can be achieved in a convenient manner.
In addition, currently available equipment is normally designed to provide a specific shot capacity which is not readily adjustable to provide a range of shot sizes. Thus, machines having large shot capacities cannot be easily adapted for use in providing smaller shot capacities, and vice-versa, so that different machines have to be available for different applications, a factor which increases the overall operating costs of a plant in which it is desired to make a variety of articles each requiring different shot capacities. Accordingly, it is desirable that such apparatus provide for adjustability of the shot capacities thereof over a reasonable range thereof.
In summary, present day equipment, particularly for providing relatively high shot capacities, does not adequately fulfill all of the above requirements, such apparatus being particularly expensive not only because of high initial costs of installation but also because of high operating costs which are due to the relatively high power requirements thereof.